Thanks for all the replies - really interesting views about NVG. Some seem to think they would help a lot, but I know some of the SAR guys who use them switch them off when doing a night rig landing at about 0.5nm and 500 RA from a rig due to excessive brightness from the rig lighting. I suppose if that's the case, then there's no real advantage, as its this final phase when things can go wrong - until .75 mm at night it's manadatory in our part A to be 4axis (or 3 if that's the max the AFCS can give) coupled, only decoupling when stable and within .75 mm.
Maybe an full NVG trial for the offshore world would be a sensible approach.